The general area to which the present matter applies is to power tools which incorporate reciprocatory motion. Examples of such tools are impact wrenches, hedge trimmers and rotary percussive drills.
In rotary percussive drills, it is known to impart percussive movement to the bit holder by means of a piston movable in a cylinder to which movement along the axis of the cylinder is imparted by suitable drive means coupled to the electric motor. The cylinder is mounted within a guide tube secured in the drill housing. However, it is found that the guide tube is subjected, during use, to a degree of vibration and differential thermal expansion and this reacts on the securing means to loosen such means when they are screws or to stress them unduly when other forms of securing means are employed.